Caddisfly Larvae (Limnephilidae) As Predators of Newt (Taricha Granulosa) Eggs: Another Player in the Coevolutionary Arms Race Revolving Around Tetrodotoxin?

Some populations of the newt Taricha granulosa possess extremely highconcentrations of the neurotoxin tetrodotoxin (TTX). Tetrodotoxin is present in adult newts and their eggs, but has been assumed to be absent from the larval stage. We testedlarval and metamorphosed juveniles for the presence of TTX and evaluated thepalatability of these developmental stages to predatory dragonfly nymphs. Alldevelopmental stages retained substantial quantities of TTX and almost all individualswere unpalatable to dragonfly nymphs. Tetrodotoxin quantity varied greatly amongindividuals. When adjusted for mass, TTX concentrations declined steadily through metamorphosis. Several juveniles were palatable to dragonflies and these individuals hadsignificantly lower TTX levels than unpalatable juveniles. These results suggest thatdespite previous assumptions, substantial quantities of TTX, originally deposited in theembryo, are retained by the developing larvae and metamorphosed juveniles and this quantity is enough to make them unpalatable to some potential predators. 3Reprinted from Toxicon, 57, Brian G. Gall, Amber N. Stokes, Susannah S. French, Elizabeth A.Schlepphorst, Edmund D. Brodie, III., and Edmund D. Brodie, Jr., Tetrodotoxin levels in larval andmetamorphosed newts (Taricha granulosa) and palatability to predatory dragonflies, 978-983, Copyright(2011), with permission from Elsevier. 58